Hi Uka!
Welcome! It sounds like what you are looking for is a “revision incisional eye-lid surgery” (doing eyelid surgery again) and possibly “epicanthoplasty” (a fancy medical word to describe surgery to either the skin folds on the inner or outer corner of the eyes)
In Korea you are definitely going to have a ton of options to choose from because cosmetic eye surgery is the most popular. Because your surgery is a revision it will tend to be slightly pricer and complicated than if it was a first or primary surgery. Also, since you are just focussing on your eyes it’s best to choose a clinic that just focusses on this area.
The prices will range depending upon the clinic, if you are Korean (Korean parents, but you live abroad) you may get access to better pricing bracket, especially at clinics that only cater to local Koreans. At larger clinics catering to foreign patients the prices may range from 1,000,000 KRW to 5,000,000 KRW (~$970 USD to $4,750 USD). It’s a pretty wide price range. And will really depend on the diagnosis.